This invention relates to a gate valve and, more particularly, to a gate valve for use with a catheter.
Catheters of the balloon type usually use one of several different types of shut-off valves. The valves are used to control the inflation and deflation of the balloon after the catheter has been placed in a desired position. It is important for the valves to present leakage during use even after extended periods of shipment and storage and to be easily handled for fast and accurate control during inflation and deflation. The valves previously provided for these purposes are usually rotary valves, pinch valves, or automatic valves. However, no shut-off valve has been found to be completely satisfactory under nearly all conditions of use with a balloon type catheter.
Rotary valves, which are also known as "plug" valves, are usually of either two-way or three-way design. The two-way design is either off or on whereas the three-way design is either off or on in two positions. These valves incorporate a rotating shaft having a lateral hole through it which can be selectively lined up with another hole or holes for the desired operating position. The two-way design as well as the three-way design are known to leak, however, especially using a gas such as carbon dioxide or air. While rotary valves are suitable in theory, the greases used with metal rotary valves tend to "creep" out of the sealing areas and the plastics used in plastic rotary valves tend to distort the sealing areas during ethylene oxide sterilization.
Pinch valves incorporate a clamp or wedge which is either off or on. The clamp or wedge is used to distort the catheter body tubing until it is occluded when the valve is in an off position. While pinch valves are relatively simple, they tend to remain permanently "off" when such valves are subjected to extended storage in an off position or are sterilized in that position.
Automatic valves incorporate an elastomeric seal inside a hub. The seal maintains the valve in an off position until a syringe is pushed into the fitting compressing the seal and opening it. While automatic valves are relatively simple, they will tend to remain open after the syringe is removed.
Catheters of the balloon type, particularly those used for hemodynamic measurements, require precise inflation and deflation of the balloon. It is particularly important to avoid overinflation and possible balloon rupture in such applications. The balloon should therefore always be deflated before injecting additional carbon dioxide or air in the event that it is believed that the balloon may have deflated to an extent to which its flow directed characteristics are lost. It is characteristic of existing shut-off valves, however, that the handling of the valve has been rather difficult and cumbersome leading to the possibility of inflation or deflation errors. While the prior art has dealt with the problems associated with valves provided for use with balloon type catheters with varying degrees of success, the present invention represents an improvement over all such prior art constructions.